Technical Abstract:
This lecture will review strategies to develop effective vaccines for several livestock diseases. It will emphasize studies aimed at defining the mechanisms of disease resistance, delineating protective immunity for each disease, and designing effective vaccines. Based on the current understanding of cytokine responses, it is clear that two major sets of cytokines are recruited in defense against infectious organisms. For the T helper 1 (Th1) responses the cytokines interferon-gamma (IFNg) and interleukin-12 (IL-12) are stimulated to activate intracellular killing mechanisms. For Th2 responses, IL-4, IL-5 and IL-10 dominate the cytokine spectrum and stimulate IgA and IgE production and mast cell and eosinophil activation. For the first disease, toxoplasmosis, I will review the rodent studies that have served as the basis for our current vaccine trials. We are currently testing whether protection can be stimulated using irradiated Toxoplasma gondii oocysts. Simultaneous studies are aimed at assessing cytokine levels stimulated by the vaccine, as compared to the challenge infection. Other diseases to be discussed are African swine fever virus infections, infections induced by transmissible gastroenteritis virus, and cryptosporidiosis. Overall, this review of vaccine trials for 4 different diseases will outline the need for targeted immune studies for each disease. Basic studies should address the specific disease pathology and define protective immunity so that effective vaccine candidates can be developed.